Discoveries demonstrate our progress, limitations

Astronomy is the great tease of the sciences: rewarding humans for their ingenuity and frustrating us with constant reminders of limits imposed by the vastness of space.

So it was last week when a team at NASA's Ames Research Center announced the discovery of two planets around a "nearby" star that are the best candidates yet discovered for harboring life.

"Nearby," however, is 12,000 light years. A light year is the distance light travels in a year, about 6 trillion miles. The numbers make it virtually certain that earthlings never will visit Kepler 62e or Kepler 62f, which are named for the extraordinary spacecraft and mission that discovered them.

Of more that 850 confirmed planets around other stars and more than 2,600 other suspected planets outside our solar system, these two are the only rocky, non-gaseous planets within the so-called "Goldilocks" zone. That's the narrow "just-right" orbital zones, like Earth's, where planets are neither too close to nor too far from their suns, where temperatures support the existence of liquid water.

Kepler 62e is 60 percent larger than Earth and has a 122-day orbit around its star. Kepler 62f is about 40 percent larger than Earth, and orbits the star every 267 days. Both planets are closer to their star than the Earth is to the sun, but the star is smaller and somewhat cooler than the sun.

That astronomers are able to make such measurements with certainty demonstrates the capabilities of modern astronomy and engineering. That those measurements will have to do demonstrates the limits, and leaves us to ponder still what lies beyond.

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